Seeking comfort with GPS

If Curt Bangasser had his way, he'd never enter his fields without being hooked up to a global positioning system (GPS).

For the past four years, this Minnesota corn and soybean farmer has used satellite-positioning technology to record and map yields, vary seed and herbicide rates and track input location by field. Each test with technology has brought him one step closer to understanding yields on his farm.

"The bottom line is profit per acre," Bangasser says. "With prices like they are, I think that comes from higher yields."

He stands with bended knee looking proudly at his 4960 John Deere tractor. By now it's fully loaded. Piece by piece, he has wired in everything he can to collect geo-referenced information about his fields, yield and inputs.

On top of the cab is a GPS antenna. Inside, a laptop teeters behind the steering console. To the right of the seat are two monitors with push-button controls. One shows his field position; the other varies chemical rates based on that field position. Hanging out the back is a box of spaghetti-like cords leading to controllers and solenoids.

Bangasser is on the cutting edge of site-specific technology. Nationally, 22% of large producers (with annual sales of more than $500,000) and 13% of mid-size producers (sales between $100,000 and $500,000) use a yield monitor with GPS, according to a recent study by the Center for Agricultural Business at Purdue University. Nineteen percent of large producers and 17% of mid-size producers use variable rate technology.

We met with Bangasser at his farm outside of Garvin, MN, and he shared how he has used satellite positioning to help make decisions about seed, chemicals and fertilizer that will result in higher yields.

Monitor yields first. Ban-gasser says that his brothers first lured him into site-specific farming. One brother is on the seed side; the other designs software. Both wanted him to test their site-specific products.

His first piece of equipment was a yield monitor with a GPS connection to track yield throughout his field. "Start with yield because that's what you're after," he says. The monitor he uses is made by Micro-Trak Systems and he says it works great. A GPS receiver by Trimble Navigation picks up satellite signals that define field location.

To reduce position error, OmniStar transmits a satellite-based differential correction signal to his farm for a monthly fee. His first year, Bangasser relied on correction signals from the U.S. Coast Guard, which are broadcast for free by radio beacons. That was a mistake. Interference from weather or his tractor's electronics caused him to frequently lose the signal. As a result, much of the yield data were misplaced on the map. "Without a good GPS, it's worthless," he adds.

After harvest, he maps the yield data on his computer using AgMapp geographical information system (GIS) software made by RDI Technologies. He says that, by mapping yields, the differences in seed varieties really stand out.

For example, last year he planted eight rows of two different varieties - Pioneer 36F30 and Golden Harvest 2390Bt - to see how yields compared. After mapping the yields, he found that the Pioneer 36F30 consistently yielded 3 to 9 bu. better. "I felt this removed practically all questionable results that you get with a small test plot, since this was virtually a 160-acre test plot."

However, he has learned that the variety that does well one year may not be the best one the next year. "I think the most important variable is the weather," he states.

The yield maps also have given him insight into tillage practices. " I've been trying to get one field moldboard plowed for the last six years following corn," he says. "Where we have not plowed, the maps are showing a 5-bu./acre yield reduction in soybeans and a 15- to 20-bu. reduction in corn." This fall he finally plowed the remaining 30 acres. "It will be interesting to see if that spot improves," he says.

Vary your seeding? In 1996, Bangasser started varying seed rates by soil type to see if the different rates increased yield or decreased seed costs. The test was part of a three-way partnership with RDI and Northrup King, which is now part of Novartis. North-rup King provided the seed and a Rawson controller to vary rates and gave Bangasser the option to buy at the end of his three-year trial.

RDI provided the variable rate software called AgMapp VR1. The software tells the controller how much seed to release to each area of the field. The user programs the rates. For example, on lighter, sandy soils, where yield potential is limited, Bangasser programmed lower populations. On more fertile ground, he programmed the maximum.

Last year was the final year of the test. His findings? "The yield monitors aren't accurate enough to really see a difference in yield. At least not yet."

As a result, he plans to quit variable rate planting. He says the only advantage he sees is reduced seed costs on marginal soil types due to lower seed populations. "I don't have enough acres of marginal soils to justify the cost," he says. "In the future I could see changing the variety to match certain soil types but will have to wait for a planter to be developed that can do it."

Spray by soil type. Using the same AgMapp VR1 software used to vary seed rates, Bangasser began varying rates of American Cyanamid's Tri-4 herbicide in his bean fields prior to planting. RDI provided the sprayer controller, a Raven 750, for testing.

"Past experience with yield maps tells me that you have to have weed control, especially grass control. So the goal here is total weed control," he explains. He programmed rates between 11/2 and 2 pints depending on the soil type. "It makes sense to lower chemical rates on hilltops and on lighter soil and put heavier amounts on lowlands to get foxtail," he says.

At the end of the season, Bangasser reported excellent grass control across the entire fields. "It's hard to say what was responsible for the excellent control," he says. "Was it the variable rateor did the herbicide work that well?"

He says he used about the same amount of herbicide with variable rate that he would have used by applying a single rate across the entire field, so he didn't save money by cutting rates. But by putting the correct rate on a particular soil type, he believes he made the most efficient use of Tri-4.

A new record function on the VR1 software allows you to make "as applied" maps that record the actual applications rather than just the programmed application. In a perfect world, the two rates would be the same. But if there's a problem with the controller, the applied rate would reveal the inconsistency and provide a more accurate record.

Map what went where. Ban-gasser started to use the feature in 1998. He wanted the "as applied" map to help him figure out why the previous year's corn yields suffered a 15-bu./acre drop in certain areas of the field, as revealed by yield maps.

"I thought the drop might have been due to spot applications of Accent. But I wasn't sure because I didn't know where I had made the applications."

So last summer he spot-sprayed Accent again, but this time used the "as applied" function to document where and what was actually sprayed. He then mapped the application and, after harvest, overlaid the "as applied" map with his yield map to see if there was a re-duction in yield in the areas he sprayed.

"I couldn't see any," Bangasser reports. "I'm not sure what happened the year before. But in the future, I will be able to go back and check the spray application maps."He feels the applied maps are an important tool. "It shows whether you applied the rate you said you did," he explains. "So if there are weeds in a certain spot, I can look at the rate I put on and determine if the sprayer skipped or if I need to increase the rate or switch chemicals."

Variable rate fertilizer. Fertil-izer on Bangasser's farm is custom applied at varying rates according to soil test results. He has his dealer make "as applied" maps of the applications.The dealer charges $7/acre for application costs alone. To reduce costs, Bangasser is thinking about applying liquid fertilizer himself using saddle tanks on his tractor and variable rate technology. However, with the high cost of equipment, he thinks he might be better off spending his dollars on more fertilizer.

Until he figures out the costs, he plans to continue to have fertilizer custom applied with variable rate or put on a straight rate himself with second appli-cations of P, K and zinc where needed.

What's Bangasser's advice for other farmers looking at satellite farming? "I would highly recommend a yield monitor with a good mapping program," he replies. "Also, be sure to get a good GPS system. Without a good GPS trail, you can't accurately analyze the yield data. It is amazing what excess water, weeds, rootworm, herbicide damage, wind, corn borers, poor stands and animal damage can do to yields."